Firstly take ukda rice and idli rice in one bowl. Rinse a couple of times in fresh water and then soak them in water for 5 hours.

Take urad dal, chana dal and ¼ teaspoon methi seeds in another bowl. Rinse a couple of times in fresh water and then soak them in water for 5 hours.

After 4 to 5 hours, Grind the urad dal, chana dal and methi seeds till you get a batter which is light and fluffy. Grind it in a fine paste. Strain the rice well and drain the water. Then in the same grinder, add the soaked rice and little water.
You can grind rice in one batch or in two batches.
Grind rice to a fine paste consistency. Also mix both the batters very well. 

Now add secret ingredient that is rice flour to the prepared batter. And mix it properly. Cover and keep aside to ferment for 8 to 9 hours.

After 8 hours, Mix the salt very well with the batter.
Now lightly stir the batter, before you begin to make dosa.

Spread the batter to a neat, round shaped thin dosa.On a medium heat, begin to cook.Then with a spoon drizzle some oil on the dosa. When the base becomes golden, the paper dosa becomes more crisp.